Check max_total_routing_fee is reduced in mpp_retry test

We check that the `RouteParameters::max_total_routing_fee` field is reduced accordingly
to our previously used fees.

Author: tnull

lightning/src/ln/functional_test_utils.rs

@@ -1878,7 +1878,11 @@ macro_rules! get_route_and_payment_hash {
 		$crate::get_route_and_payment_hash!($send_node, $recv_node, payment_params, $recv_value)
 	}};
 	($send_node: expr, $recv_node: expr, $payment_params: expr, $recv_value: expr) => {{
-		let route_params = $crate::routing::router::RouteParameters::from_payment_params_and_value($payment_params, $recv_value);
+		$crate::get_route_and_payment_hash!($send_node, $recv_node, $payment_params, $recv_value, None)
+	}};
+	($send_node: expr, $recv_node: expr, $payment_params: expr, $recv_value: expr, $max_total_routing_fee_msat: expr) => {{
+		let mut route_params = $crate::routing::router::RouteParameters::from_payment_params_and_value($payment_params, $recv_value);
+		route_params.max_total_routing_fee_msat = $max_total_routing_fee_msat;
 		let (payment_preimage, payment_hash, payment_secret) =
 			$crate::ln::functional_test_utils::get_payment_preimage_hash(&$recv_node, Some($recv_value), None);
 		let route = $crate::ln::functional_test_utils::get_route(&$send_node, &route_params);

lightning/src/ln/payment_tests.rs

@@ -83,7 +83,11 @@ fn mpp_retry() {
 	send_payment(&nodes[3], &vec!(&nodes[2])[..], 1_500_000);
 
 	let amt_msat = 1_000_000;
-	let (mut route, payment_hash, payment_preimage, payment_secret) = get_route_and_payment_hash!(nodes[0], nodes[3], amt_msat);
+	let max_total_routing_fee_msat = 50_000;
+	let payment_params = PaymentParameters::from_node_id(nodes[3].node.get_our_node_id(), TEST_FINAL_CLTV)
+		.with_bolt11_features(nodes[3].node.invoice_features()).unwrap();
+	let (mut route, payment_hash, payment_preimage, payment_secret) = get_route_and_payment_hash!(
+		nodes[0], nodes[3], payment_params, amt_msat, Some(max_total_routing_fee_msat));
 	let path = route.paths[0].clone();
 	route.paths.push(path);
 	route.paths[0].hops[0].pubkey = nodes[1].node.get_our_node_id();
@@ -150,6 +154,9 @@ fn mpp_retry() {
 	route.paths.remove(0);
 	route_params.final_value_msat = 1_000_000;
 	route_params.payment_params.previously_failed_channels.push(chan_4_update.contents.short_channel_id);
+	// Check the remaining max total routing fee for the second attempt is 50_000 - 1_000 msat fee
+	// used by the first path
+	route_params.max_total_routing_fee_msat = Some(max_total_routing_fee_msat - 1_000);
 	nodes[0].router.expect_find_route(route_params, Ok(route));
 	nodes[0].node.process_pending_htlc_forwards();
 	check_added_monitors!(nodes[0], 1);